"There is no scientific evidence available that can substantiate their claims at the moment," said Bruintjes, lead researcher of the Colorado-based National Center for Atmospheric Research's international weather-modification programs.

He remains confident about the potential of weather modification, which has long been hyped as a means of building water supplies and disrupting dangerous storms.

Bruintjes spoke Tuesday at an international meeting on weather modification in Westminster, Colorado. He and colleagues suggested that new computer technologies, weather satellites, Doppler radar and other advances may open an new era of human-modified weather.

Long History

Human efforts to manipulate the weather have a long history.

Scientists have been trying to seed clouds and produce rain since the mid-1940s. During the Vietnam War, the U.S. military even tried to swamp the Ho Chi Minh Trail by producing torrential rains.

Military use of weather modification has since been banned by an international treaty since 1978.

China's ambitious Olympic plan is just a small part its weather modification program, the world's largest.